A current microwave transmission apparatus usually adopts a separated system structure. As shown in FIG. 1, a microwave transmission apparatus includes an indoor unit (IDU) and an outdoor unit (ODU). Interaction of service signals, communications signals, and power supply signals is implemented through an interconnected coaxial cable between the IDU and the ODU.
In the following, FIG. 1 is illustrated with processing methods of the microwave transmission apparatus on a service signal and a communication signal. The microwave transmission apparatus processes the signals in two signal processing directions, that is, an uplink direction and a downlink direction, where the uplink direction refers to the signal processing direction from the IDU to the ODU, and the downlink direction refers to the signal processing direction from the ODU to the IDU.
The processing on a service signal in the uplink processing direction mainly includes the following steps.
In step S1, a digital modern module in the IDU modulates the service signal to an intermediate frequency (IF) (for example, 350 MHz), to obtain an uplink IF signal, and sends the uplink IF signal to an uplink analog IF module.
In step S2, the uplink analog IF module filters and amplifies the uplink IF signal appropriately, and sends the processed uplink IF signal to a signal combining and dividing module.
In step S3, the signal combining and dividing module in the IDU multiplexes the processed uplink IF signal with other signals (for example, a communications signal), and sends the multiplexed signal to a coaxial cable to be transmitted to the ODU.
In step S4, the signal combining and dividing module in the ODU receives the multiplexed signal, strips the uplink IF signal out, and sends the stripped signal to an IF AGC module in the ODU.
In step S5, the IF AGC module in the ODU compensates attenuation of the uplink IF signal in the coaxial cable, and sends the compensated uplink IF signal having a relatively constant power to a frequency converting module in the ODU.
In step S6, the frequency converting module performs frequency conversion on the uplink IF signal to convert the IF frequency into a radio frequency (RF), and sends the RF signal to an amplifying module to be amplified and transmitted to a free space through an antenna.
The processing on the service signal in the downlink processing direction mainly includes the following steps.
In step S7, the ODU receives the RF signal from the free space through an antenna, then amplifies the RF signal, and sends the signal to the frequency converting module. The frequency converting module performs frequency conversion on the amplified RF signal to convert its frequency into an IF frequency (for example, 140 MHz), to obtain a downlink IF signal, and sends the downlink IF signal to the IF AGC module in the ODU.
In step S8, the IF AGC module compensates attenuation of the RF signal in the free space, and sends the compensated downlink IF signal having a relatively constant power to the signal combining and dividing module in the ODU.
In step S9, the signal combining and dividing module in the ODU multiplexes the downlink IF signal with other signals (for example, a communications signal), and transmits the multiplexed signal to the IDU through a coaxial cable.
In step S10, the signal combining and dividing module in the IDU receives the multiplexed signal, strips the downlink IF signal out, and sends the stripped signal to an IF AGC module in the IDU.
In step S11, the IF AGC module in the IDU compensates attenuation of the downlink IF signal in the coaxial cable, then sends the compensated downlink IF signal having a relatively constant power to a downlink analog IF module, and sends the processed signal to a digital modem module for demodulation, to obtain a demodulated service signal.
The processing on a communications signal in the uplink processing direction mainly includes the following steps.
In step T1, a digital part of communications circuit in the IDU sends a digital communications signal to a analog part of communications circuit, and the analog part of communications circuit converts the digital communications signal into an analog communications signal, modulates the analog communications signal to an appropriate frequency (for example, 5.5 MHz), to obtain an uplink communications signal, and sends the uplink communications signal to a signal combining and dividing module in the IDU.
In step T2, the signal combining and dividing module in the IDU multiplexes the uplink communications signal with other signals (for example, a service signal), and transmits the multiplexed signal to the ODU through a coaxial cable.
In step T3, the signal combining and dividing module in the ODU strips the uplink communications signal from the multiplexed signal, and sends the stripped signal to an analog part of communications circuit in the ODU.
In step T4, the analog part of communications circuit in the ODU demodulates the uplink communications signal, and sends the demodulated uplink communications signal into a digital part of communications circuit.
The processing on the communications signal in the downlink processing direction is substantially similar to that in the uplink direction, and a difference mainly lies in that the frequency of the downlink communications signal obtained by the communications circuit analog part in the ODU is different from that of the uplink communications signal (for example, 10 MHz).
During the processing of the microwave transmission apparatus on the service signal and the communications signal, a signal combining and dividing module is configured to multiplex two types of signals together in the signal combining and dividing mode by performing frequency division multiplexing in the prior art, and the multiplexed signal is transmitted by a cable in common.
In the implementation of the present invention, the inventor found that the prior art has at least the following problems. In the prior art, a service signal is modulated or demodulated by a digital modem module in an IDU, and the service signal is transmitted or received by an antenna in an ODU, so that the signal-to-noise ratio of the service signal is too low, which is caused by the long distance between the digital modem module and the antenna is too long.